U.S. auto sales accelerated to a blistering pace in September as strong Labor Day weekend deals sweetened results for the Detroit Three and put the auto industry in a position to achieve its best year of sales since 2000. General Motors Co., Fiat Chrysler Automobiles NV and Ford Motor Co. each posted double-digit percentage increases over a year ago as buyers splurged on pickup trucks and sport-utility vehicles. They project the overall sales pace for September will top 18 million vehicles on a seasonally adjusted annualized selling rate. GM’s forecast calls for a pace as high as 18.3 million vehicles for September, a level not seen since July 2005. Car sales gains are being fueled by low interest rates, cheap gasoline and a strengthening labor market. The September numbers also received an unusual lift from a late Labor Day weekend. A year ago, most Labor Day weekend sales bolstered August results. Sales of the German auto giant’s Audi brand rose in the U.S. in September and it predicted strong demand in coming months despite the group’s manipulation of emissions. Audi sold 17,340 vehicles in September, up 16% over a year earlier. For the month, auto sales should increase 12% year-over-year to a total of 1.39 million vehicles, according to researcher Kelley Blue Book. The average new-vehicle transaction price was expected to hit $33,730 for the month, an increase of $660 from the same period a year earlier.